1. Field of the Invention
The present invention is directed in general to semiconductor devices and methods for manufacturing same. In one aspect, the present invention relates to the fabrication of semiconductor devices or integrated circuits which use optical communication circuits and devices.
2. Description of the Related Art
In information systems, data signal information is communicated between devices and circuits using different types of signal connections. With electrical conductor-based connections, such as conventional wires or through silicon vias (TSVs), there are power and bandwidth constraints imposed by the power requirements and physical limitations of such conductor-based connections. For example, stacked die modules have been proposed to provide high density information systems, but the power consumption and associated heat dissipation requirements for communicating data signals between stacked die modules using conductor-based connections can limit the achievable density. In addition, the bandwidth of such stacked die modules is limited by the number and inductance of TSVs and other conductor-based connections for such die stacks. To overcome such limitations, optical communication systems have been developed as a way of communicating at higher bandwidths with reduced power. With such optical communication systems, a monochromatic, directional, and coherent laser light beam is modulated to encode information for transfer to other devices or circuits of the system, typically by including a laser beam light source and modulator on each die transferring modulated light signals along one or more optical fiber or waveguide paths formed on the die. Unfortunately, there are design and implementation challenges presented with using optical waveguides to transfer optical information between different integrated circuit (IC) chips in a system in terms of cost, complexity, and control requirements. These challenges arise from integrating laser diode fabrication technology with CMOS logic fabrication technology, both in terms of the different materials and fabrication processes used to make laser diodes and logic devices, but also in terms of the relative complexities of the different types of devices. Even when the fabrication challenges for integrating optical and electrical circuit elements on a single die are overcome, there are additional costs and challenges with routing optical signal information to different die in a die stack in terms of fabricating and aligning optical signal paths across the die stack, as well as design complexity challenges of integrating optical and electrical circuits on each die. As a result, the existing solutions for transferring modulated light signals along optical waveguide paths and between different IC chips make the implementation of high bandwidth optical interconnects extremely difficult at a practical level.
It will be appreciated that for simplicity and clarity of illustration, elements illustrated in the drawings have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to other elements for purposes of promoting and improving clarity and understanding. Further, where considered appropriate, reference numerals have been repeated among the drawings to represent corresponding or analogous elements.